Socket connector with contact terminal having waveform arrangement adjacent to tail portion perfecting solder joint

ABSTRACT

An electrical connector includes an insulative housing with a number of through holes extending therethrough, a number of contacts assembled to the insulative housing, and a number of solder balls disposed in the though holes and each is clasped by the tail and insulative housing. Each contact includes a vertical base portion secured to a first side of the through hole, a contact engaging arm extending from a top end of the base portion, and a solder portion extending from a bottom end of the base portion. The solder portion has a wave arrangement below the base portion and projecting from the base portion to a second side of the through hole which opposites to said first side, and a tail extending downwardly from the wave arrangement and capable of moving from the first side to the second side.

This application is a continuation-in-part of a patent application Ser.No. 12/763,226 entitled “Socket Connector With Contact Terminal HavingWaveform Arrangement Adjacent To Tail Portion Perfecting Solder Joint”filed on Apr. 20, 2010.

FIELD OF THE INVENTION

The present invention relates to a socket connector, and moreparticularly to a socket connector incorporated with a contact terminalhaving a wave arrangement adjacent to a tail portion of the contactterminal so as to perfect solder joint resulting from this wavearrangement.

DESCRIPTION OF PRIOR ART

Soldering between a solder tail of a contact terminal and a conductivepad on a printed circuit board is comparably reliable and commonpractice in the electrical connector field. When conducting a solderingprocess, there is s dilemma. At one hand, it is requested that thesolder tail expresses solderable property, i.e. the solder can bereadily and easily attached thereto. If the solder joint is not properlyformed between the solder tail and the printed circuit board, defectiveinterconnection or so called cold-joint will be encounter. Reworkprocess will always be needed to correct this problem. On the otherhand, because of this solderable property, the solder tends to flowupward or wick along an external surface of the solder tail. Once thesolder flows and wicks upwardly along the surface resulted from thecapillary force, the overall characteristic of the contact terminal willbe changed or negatively modified. For example, when the contactterminal is designed, intended normal force, deflection, etc have beencarefully calculated so as to meet the field requirements. Once thesolder flows and wicks upward to cover the contact terminal, thecharacteristic of the contact terminal will be altered, and the normalforce and other properties will be altered accordingly. In worsesinario, a connector after soldering will be found failed resulted fromthis solder wicking. As a result, the contact terminal is requested toprovide a mechanism to limit the wicking.

U.S. Pat. No. 4,019,803 issued to Schnell on Apr. 26, 1977 disclosed asolder substrate clip having a contact arm. A mass of solder is securedto the arm on a side away from a contact surface and a solder globuleintegral with the mass of solder at an edge of the arm extending fromthe mass across the edge of the arm to the contact surface forengagement with a contact pad on the substrate.

U.S. Pat. No. 4,846,734 issued to Lytle on Jul. 11, 1989 discloses aconnector featuring that a connector adapted to be attached to a motherprinted circuit board and to removably receive a daughter printedcircuit board of the edge card type and adapted to mechanically andelectrically couple the mother and daughter printed circuit boards.According to its disclosure, the invention may be incorporated into amethod to make the contact terminal and which further includes the stepof fabricating the contact of phosphor bronze. The method furtherincludes the step of plating the contact with nickel to a thickness ofabout between 0.000050 and 0.000150 inches. The method further includesthe step of plating the lower portion of the contact with solder ofabout 60 percent tin and 40 percent lead to a thickness of about between0.000100 and 0.000500 inches. The method further includes the step ofplating the contact portion of the contact with about 40 microinchesthick or thicker of PdNi flashed with gold to a thickness of about0.000004 inches nominally. It is known to the skilled in the art thattin-lead is solderable material, while nickel oxide is non-solderable.Because of that, a tin-lead coating is applied to the lower portion.

U.S. Pat. No. 5,453,017 issued to Belopolsky on Sep. 26, 1995expressivebly take the advantage of the benefit disclosed in Lytle. InBelopolsky, it discloses an improved connector for an electronic moduleor the like and includes a housing having a socket opening that is sizedand configured to accept an electronic module, and a plurality ofterminals mounted to the housing. Each of the terminals has a footportion having a layer of non-solderable material coated on one side ofthe foot portion to prevent solder from adhering to that side. Acapillary nest is formed by a channel surface on the underside of thefoot portion when the terminal is mounted on a conductor pad such thatsolder flows through the capillary nest under the influence of capillaryforces from the side of the terminal having a non-solderable coatingthereon to the other side for forming a solder joint on that other side.A ring of non-solderable material is coated around a middle portion ofthe terminal to prevent solder from flowing to the electrical contactsurfaces located above the ring. As a result, the connector terminalscan be soldered to a printed circuit board or the like in a simple andinexpensive manner and without the formation of known solder defects. Asdisclosed by Belopolsky, solderable material used in capillary nest isto promote solderability on the solder tail, while the non-solderablering located at the middle portion limits the solder from wickingfurther upward.

U.S. Pat. No. 4,722,470 issued to Johary on Feb. 2, 1988 disclosesanother mechanism to overcome or control the solder wicking. Accordingto Johary, a solder transfer member for applying discrete bodies ofsolder of predetermined size to the leads of a component for subsequentsurface mounting to a substrate. The transfer member is a plate having anon-wetted surface, for example titanium, with an array of cavitiesmatching the component lead pattern, each having a volume correspondingto the desired amount of solder to be applied to the corresponding lead.The method includes placing solder paste on the transfer member andfilling the cavities by wiping the plate surface. The component isplaced on the transfer member with the leads contacting the solder pastein the cavities. Reflow of the solder paste bonds to each lead adiscrete body of solder having a precisely determined size. To limitwicking of solder on the leads, selective masking may be performed byapplying a water soluble mask coating to the leads and removing the maskfrom selected areas by placing the component against a surface chargedwith water before placing the component on the transfer member.

U.S. Pat. No. 6,042,389 issued to Lemke on Mar. 28, 2000 disclosedanother mechanism to limit the solder wicking issue. According to FIG.6, along with description, “The opening 96 also can function as athermal break to retard solder wicking, in the same manner as openings89 in the FIG. 6 embodiment. The terminal 90 may also includepassivation or anti-wicking coatings to prevent solder flow toward thecontact sections. Aperture or opening 89 defined in the contact tail 76is used to limit the wicking issue.”

U.S. Pat. No. 4,019,803 issued to Schnell on Apr. 26, 1977 discloses asolder substrate clip having a contact arm, a mass of solder secured tothe arm on a side away from a contact surface and a solder globuleintegral with the mass of solder at an edge of the arm extending fromthe mass across the edge of the arm to the contact surface forengagement with a contact pad on the substrate. According to itsdescription, along with FIGS. 1 to 4, it looks like that Schnell usesenergy to control the wicking issue. According to Schnell, the amount ofenergy supplied to the interface between the solder mass and the arm issufficient to melt the entire mass, in that way assuring that arelatively large mass of molten solder does not coat the contact surfaceof the arm. While molten solder does not readily flow across the rawuncoated edges, a relatively large amount of molten solder could flowacross the edges and coat the contact surface. This is undesirablebecause when a substrate is moved into the mouth the arms are bentfurther apart than intended due to the thickness of the solder coatingand may be overstressed. During soldering of the clip to the substrate,the thick layer of solder would be melted freeing the arms for undesiredmovement during the soldering operation. Overstressed arms may not bestrong enough to engage the substrate tightly.

U.S. Pat. No. 4,120,558 issued to Seidler on Oct. 17, 1978 disclosesanother way, as compared to Lemke and Schnell, to attach the solder massto the contact. Seidler uses spring fingers to mechanically hold thesolder mass, such as shown in FIGS. 1 to 5, and 13 to 15. According toSeidler, each clip includes a flat body portion 15, a pair of springfingers 16, bent to extend upwardly and laterally from the plane of thebody portion distally of the clip and spaced apart by the width of acentral spring finger 17 which extends laterally in a position spacedfrom and substantially parallel to the fingers 16, defining a gap 21adapted to receive the edge of a substrate (not shown). The fingers 16and 17 are formed from the blank shown in FIG. 4 by the parallel cuts 18which terminate at end points 18′. An additional gripping finger 19 isprovided by the U-shaped cut 20, the sides of which lie parallel to thecuts 18 and the closed end 20′ being below the line of the ends 18′,this finger thus being formed partially from the material in the centralfinger 17. The free end of the finger 17 is curved arcuately away fromthe finger 16, and the gripping finger 19 is curved arcuately toward thecurved end of finger 17, in a position to grip securely the shortcylindrical slug of solder 22, as clearly shown in FIGS. 1, 2 and 3.

U.S. Pat. No. 6,969,286 issued to Mongold on Nov. 29, 2005 disclosesanother type of mechanism to attach the solder mass to the solder tail.According to Mongold, an electrical connector includes a connector body,a plurality of cores and a plurality of electrically conductive contactsdisposed in the cores of the connector body. Each of the contactsincludes a fusible member attached thereto. Each of the fusible membersincludes an intermediate portion and two support members disposed onopposite sides of the intermediate portion. The support members arearranged to hang down below a tail portion of the contacts. Asillustrated in FIG. 1B, it looks like the solder mass 40 a, 40 b isattached to the contact terminal 22 in a manner of a landing gear of anairplane. According to Mongold, each fusible member 40 has two supportportions 40 a, 40 b which are connected to each other by an intermediateportion 40 c. The two support portions 40 a, 40 b are disposed oppositeto each other and spaced from each other by a distance that is equal toa length of the intermediate portion 40 c. The two support portions 40a, 40 b may preferably have substantially flattened bottom surfaces asshown in FIG. 1B. However, the bottom surfaces of the support portions40 a, 40 b may also have other shapes such as rounded, spherical,conical, square, rectangular, and other suitable shapes.

Chinese Utility Model Patent No. CN2618319Y published on May 26, 2004discloses an arrangement in which both the contact and housing is usedto hold the solder mass thereto. This arrangement is similar to whatillustrated by Seidler, and Schnell, while the housing of the connectorbody is also used.

U.S. Pat. No. 6,572,397 issued to Ju on Jun. 3, 2003 discloses anotherarrangement in which the solder mass is held by a cuverlinear portion ofa solder tail.

US Pat Pub No. 20070293060 submitted by Ju discloses another arrangementin which a cradle-shaped portion is used to hold the solder mass.

Chinese Utility Model Patent No. CN2718822Y published on Aug. 17, 2005discloses an arrangement in which two contact terminals are arrangedwithin a single passageway and a solder ball is held by two solder tailsof the contact terminals.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a connector socketwith an array of contact terminals arranged therein and featured thateach of the contact terminal is provided with a curvilinear tail portionand an encampment adjacent to a passageway such that a solder mass canbe readily and reliably positioned therebetween.

Disclosed herewith An electrical connector comprises an insulativehousing having opposite upper and lower surfaces and a plurality ofthrough holes extending through the upper surface to the lower surface;a plurality of contacts assembled to the insulative housing; and aplurality of solder balls disposed in the though holes and each isclasped by the tail and insulative housing. Each contact includes avertical base portion secured to a first side of the through hole, acontact engaging arm extending from a top end of the base portion, and asolder portion extending from a bottom end of the base portion, saidsolder portion including a wave arrangement below the base portion andprojecting from the base portion to a second side of the through holewhich opposites to said first side, and a tail extending downwardly fromthe wave arrangement and capable of moving from the first side to thesecond side.

Still according to one of the aspects of the present invention, Thethrough hole comprises an upper passageway and a lower retaining slotcommunicated with each other. A plurality of solder members each issecured by one side of the retaining slot and the tail. The tail and theother side of the retaining slot define a deforming space so that thetail can move to the other side of the retaining slot to dispose thesolder member.

BRIEF DESCRIPTION OF DRAWINGS

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention, togetherwith its objects and the advantages thereof, may be best understood byreference to the following description taken in conjunction with theaccompanying drawings, in which like reference numerals identify likeelements in the figures and in which:

FIG. 1 is an exploded perspective view of a partially-shown socketconnector made in accordance with a first embodiment of the presentinvention;

FIG. 1A is a top view of the socket connector shown in FIG. 1;

FIG. 2 is a perspective view of the partially-shown socket connectortaken from a bottom and showing a contact has been assembled into thesocket connector, while the solder ball is still unsecured thereto;

FIG. 3 is similar to FIG. 2, only with the solder ball secured between asolder tail of the contact and an edge of a passageway of the socketconnector;

FIG. 4 is a cross sectional view of the partially-shown socket connectorshowing the solder ball is securely retained between the solder tail ofthe contact and the edge of the passageway of the socket connector;

FIG. 5 is a side view of the partially-shown socket connector;

FIG. 6 is an exploded perspective view of a partially-shown socketconnector made in accordance with a second embodiment of the presentinvention;

FIG. 6A is a top view of the socket connector shown in FIG. 6;

FIG. 6B is a side view of a solder portion of a contact terminal of thesocket connector shown in FIG. 6;

FIG. 7 is an assembled view of the partially shown socket connector inFIG. 6;

FIG. 8 is a cross sectional view showing a solder ball is held betweenedges and a solder tail of the contact terminal shown in FIG. 6;

FIG. 9 is a side elevation view of the contact terminal along with thesolder ball retained, while the insulative housing is shown in dottedline;

FIG. 9A is an enlarged view of a part of the contact terminal in FIG. 9marked with circle;

FIG. 10 is similar to FIG. 9 with the solder ball reflowed, and creatinga tear-drop shaped solder joint embedding the curvilinear lobe of thecontact terminals, the first slope, and portion of the peak of the wavearrangement;

FIG. 11 is a perspective view of a partially shown socket connector inaccordance to a third embodiment of the present invention;

FIG. 11A is a top view of the socket connector shown in FIG. 11;

FIG. 12 is a perspective bottom view of the insulative housing shown inFIG. 11;

FIG. 13 is an illustration showing the solder ball is reaching to aposition defined between the curvilinear lobe and the housing;

FIG. 14 is similar to FIG. 13, while the solder ball reaches to itsfinal position;

FIG. 15 is a top view of FIG. 11 with a pair of contact terminals isshown;

FIG. 16 is a side elevational view of a contact terminal made inaccordance with a fourth embodiment of the present invention showing asolder notch is defined in the solder portion;

FIG. 17 is a also a side elevational view, turning 90 degrees, showing asolder notch is embedded by the solder joint;

FIG. 18 is a bottom view of a socket connector made in accordance to afourth embodiment of the present invention;

FIG. 19 is a cross sectional view of a passageway showing a relationshipbetween a lower portion of the passageway, a curvilinear solder portiondisposed in the passageway, and a solder ball properly secured betweenthe lower portion of the passageway and the curvilinear solder portion;

FIG. 20 is a perspective view of a socket connector implemented thefeatures of the current invention in which contact engaging arms arepartially shown for illustration; and

FIG. 21 is a bottom view of the socket connector shown in FIG. 20.

FIG. 22 is a perspective view of an electrical connector in accordancewith a fifth embodiment of the present invention;

FIG. 23 is an exploded perspective view of the electrical connectorshown in FIG. 22;

FIG. 24 is another exploded perspective view of the electrical connectorof FIG. 22 taken from a different angle;

FIG. 25 is a cross-sectional view taken along line 22-22 of FIG. 22;

FIG. 26 is similar to FIG. 25 but taken from a different angle;

FIG. 27A is an enlarged view of the circle portion of FIG. 26; and

FIG. 27B is similar to FIG. 27A while illustrates the tail of thecontact deformed during disposing the solder ball.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, a partially-shown socket connector 1 made inaccordance with a first embodiment is shown. In generally, the socketconnector 1 is substantially similar to the U.S. Pat. No. 6,877,990issued to Liao et al. on Apr. 12, 2005; U.S. Pat. No. 6,908,313 issuedto Walkup et al. on Jun. 21, 2005, which are both referred to as LGAsocket connector. For a clear and concise description, only a singlepassageway 10, a single contact 20 and a solder ball 30 are disclosed,as it can be merely duplicated into an array of socket connector such asdescribed in U.S. Pat. No. 7,044,746 issued to Copper et al. on May 16,2006.

As shown in FIGS. 1 and 1A, the socket connector 1 includes aninsulative housing 10 defining an array of passageways 11 which has aretaining slot 12 in communication with the corresponding passageway 11.Within each and every passageway 11, a contact terminal 20 is assembledtherein. The contact terminal 20 includes a base portion 21 with aretaining section 22 extending therefrom, and which are both securelyretained within the retaining slot 12. A contact engaging arm 23 extendsfrom the retaining section 22 which further includes a contact tip 24for electrical contact with a conductive pad of an IC package. Theextension of the contact engaging arm 23 from the retaining section 22give a robust flexibility of the contact engaging arm 23 when which isin contact with the conductive pad. The contact terminal 20 furtherincludes a solder portion 25 extending downward from the base portion21, and a curvilinear lobe 26 having a tip 26 a is formed. A solder ball30 is then snuggly secured between an edge 11 a of the passageway 11 andthe tip 26 a of the solder tail 26. See FIGS. 3, 4 and 5.

As it can be readily seen from the illustration of FIG. 4, the baseportion 21 and the retaining section 22 are both securely retainedwithin the retaining slot 12, while the contact engaging arm 23 ispartially disposed within the passageway 11 and partially extends out ofthe passageway 11, specially the contact tip 24. In order to have thesolder ball 30 securely retained there, a center C of the solder ball 30is disposed above a line drawn between the tip 26 a of the curvilinearlobe 26 and the edge 11 a of the passageway 11. After the solder ball 30is secured, portion of the solder ball 30 extends into the passageway11.

Now referring to FIGS. 6 through 10, a partially-disclosed socketconnector A1 made in accordance with a second embodiment is shown. Asshown in FIGS. 6 and 6A, the socket connector A1 includes an insulativehousing A10 defining an array of passageways A11 which has a retainingslot A12 in communication with the corresponding passageway 11. Withineach and every passageway A11, a contact terminal A20 is assembledtherein. Similar to the contact terminal 20 shown in the firstembodiment, the contact terminal A20 includes a base portion A21 with aretaining section A22 extending therefrom, and which are both securelyretained within the retaining slot A12. A contact engaging arm A23extends from the retaining section A22 which further includes a contacttip A24 for electrical contact with a conductive pad of an IC package.The extension of the contact engaging arm A23 from the retaining sectionA22 give a robust flexibility of the contact engaging arm A23 when whichis in contact with the conductive pad. The contact terminal A20 furtherincludes a solder portion A25 extending downward from the base portionA21, and a curvilinear lobe A26 having a tip A26 a is formed. A solderball A30 is then snuggly secured between an edge A11 a of the passageway11 and the tip A26 a of the solder tail A26. In this embodiment, theedge A11 a is a curvilinear edge. The housing A10 further includes amating interface A13 with a pair of standoff A14 and A14 a associatedwith each of the passageway A11. The provision of the standoff A14 andA14 a will prevent the contact engaging arm A23 from collapsing in caseexcessive work load is inadvertently exerted to the contact engaging armA23.

Now specially draw to the attention of FIGS. 9 and 10, the solderportion A25 includes a wave arrangement A27 in a middle thereof andwhich includes a peak A271, a first slope A272 and a second slope A273.Since the peak A271 projects toward the solder ball A30, accordingly, anedge A301 of the solder ball A30 is substantially surrounded by the peakA271, the first slope A272, and the tip A26 a of the cuviliner lobe A26.By this arrangement, the contact area between the solder portion A25 andthe solder ball A30 is preferably increased and which benefits a latersurface mount process in which the socket connector A1 is soldered ontoa printed circuit board.

The wave arrangement A27 in fact benefits the formation of an idealsolder joint, as shown in FIG. 10, i.e. a tear-drop shaped solder joint,a comparably enlarged base, while a convergent top. During the reflowingprocess, once the solder ball A30 is liquidated or in liquid form, thesurface tension will draw the molten solder to flow along the firstslope A272 and this capillary action will ensure that the first slopeA272 along with the curvilinear lobe A26 to be completely embeddedwithin the solder joint which featured an enlarged base. However, oncethe molten solder flows to the peak A271, because of the second slopeA273 is opposite to the first slope A272 or symmetrical to the firstslope A272 centered on the peak A271, the surface tension of the moltensolder will not benefit the molten solder to flow further upward, i.e.the molten solder will be substantially limited to flow further upwardaround the peak A271. Accordingly, not only will the wave arrangementA27 feature a robust and reliable solder joint, but also will providewicking retarding effect.

Specially, as shown in FIG. 9, the peak A271, the tip A26 a of thecurvilinear lobe A26 and the edge A11 a of the passageway A11 configurejointly an equilateral triangle as seen from side elevational view, andmost of the solder ball A30 is disposed within this equilateraltriangle, no mention that the center of the solder ball A30 is alsolocated within this equilateral triangle.

In this embodiment, it can be readily appreciated that curvilinear edgeA11 a and curvilinear lobe A26 properly cradle the solder ball A30therebetween. In fact, the curvilinear edge A11 a provides a horizontalsupport or limitation, while the curvilinear lobe A26 along with thepeak A271 of the wave arrangement A27 provides a vertical support orlimitation. Accordingly, the solder ball A30 is securely and robustlycradled between those two curvilinear supports, i.e. curvilinear edgeA11 a, and curvilinear lobe 26. Because the solder ball A30 is heldbetween two curvilinear edges, the deformation or damage to the solderball A30 during this mechanic ball attachment process is tremendousreduced, and which benefits and perfects a robust and reliable solderjoint, the tear-drop solder joint such as disclosed in FIG. 10.

Now referring to FIGS. 11 to 14, a socket connector B1 made inaccordance with a third embodiment of the present invention. In thisembodiment, a mating interface B13 of the insulative housing B10 isprovided with a standoff B14 associated with the tip B24 of the contactengaging portion B23. The provision of the standoff B14 is to preventthe contact engaging portion B23 from collapsed resulted from excessiveload from the IC package. From the top view of FIG. 11A, it can bereadily appreciated that each tip B24 of the contact engaging portionB23 is associated with the standoff B14.

As disclosed in the first and second embodiments, after the solder ball30 (A30) is secured between the housing 10 (A10) and the solder portion25 (A25), a portion of the solder ball 25 (A25) is disposed within thepassageway 11 (A11). In fact, the more the solder ball 30 (A30) isdisposed within the passageway 11 (A11), the more secured relationshipbetween the solder ball 30 (A30), the edge 11 a (A11 a) of thepassageway 11 (A11), and the tip 26 a (A26 a) of the curvilinear lobe 26(A26). However, this creates a problem for the solder ball 30 (A30) tomove into final position. Accordingly, measurement has been provided toresolve this issue.

Now referring to FIGS. 12, 13 and 14, the insulative housing B10 of thesocket connector B1 made in accordance with a third embodiment of thepresent invention defines a mounting interface B15 and a ball notch B16is provided in adjacent to the passageway B11. Accordingly, when thesolder ball B30 is inserted into the space defined between the edge B11a of the passageway B11, the peak B271 and the tip B26 a of thecurvilinear lobe B26, the ball notch B16 will smooth the insertion ofthe solder ball B30. On the other hand, an inner wall of the passagewayB11 adjacent to the solder portion B26 is defined with a recess B17 forthe yielding of the solder portion B26 when the solder ball B30 isreached to its final position, such as shown in FIGS. 14 and 15. Sincethe contact terminal B20 is made from resilient material, during thereflowing process, once the solder ball B30 reaches to its molten state,when the solder portion B26 will resume to a proper position, such asillustrated in FIG. 10, a perfect tear-drop solder joint with the solderportion B26 properly embedded within the solder joint.

According to another feature of the third embodiment of the socketconnector B1, an inclined surface B18 runs between the lower edge B11 aand an inner wall of the passageway B11 in a manner such that the solderball B30 can be readily and effectively move into its final position, asshown in FIGS. 12, 13 and 14. By this arrangement, not only can thesitting of the solder ball B30 be readily done, but also provide asurface contact between the solder ball B30 and the inclined surfaceB18.

Referring now to FIGS. 16 and 17, according to a fourth embodiment ofthe present invention, a solder notch C28 is defined in a solder portionC26 of a contact terminal C20. As shown in FIG. 17, once a solder ballC30 is melted, the solder notch C28 will be completely embedded withinthe solder joint such that a robust and reliable interconnection betweenthe contact terminal C20 and a printed circuit board C40 is readilyachieved.

The contact terminals described above through different embodiments canbe readily and conveniently fabricated with the following steps,including the steps of initially providing an elongate strip ofelectrically conductive material stamped from a sheet with a lowerportion, an upper portion and intermediate contact portions. The stripis then going through different work stations such that all thoseconfigurations, such as the contact engaging arm, the base portion andthe curvilinear solder portion including all the details can beconsecutively created. The contact terminal is kept connected to acarrier of the strip for cleaning and plating. The contact terminals areremoved or severed after each and every contact terminals are assembledto a connector housing.

Before the contact terminals can be assembled and inserted into thepassageways defined in the connector housing, since the contactterminals is made from phosphor bronze or the like, it is necessary tohave it treated with certain nominal processes, including plating thestrip along with the contact terminals with a layer of nickel to athickness of nominal thickness. Then, the contact engaging arm ispartially plated with nobel metal, such as gold, and palladium or thelike for ensuring reliable interconnection with a mated electronicdevice. Normally, the solder portion or curvilinear lobe can be readyfor receiving solder ball thereto since the solder ball can be properlyfused to the nickel layer if the solder ball is fused to the solderportion not long after the connector is manufactured. However, since thepresent invention features a mechanic attachment of the solder ball tothe solder portion, the solder ball may not be fused to the solder tailright after the connector is manufactured. It properly will wait sometime on the shelf till the connector is mounted to a mother boardthrough the soldering process. Nevertheless, once the nickel layer is incontact with the oxygen in the air, the nickel layer is oxidated intonickel oxide which makes the solder ball a little bit difficult to befused to. In order to over come this inadvertent phenomenal and ensure arobust and reliable fusion between the solder ball and the solderportion, a layer of tin, or gold can be plated onto the solder portionto ensure the solder ball to be readily and reliably fused thereto, ofcourse including the mother board.

Now referring to FIGS. 18 and 19, a partially shown socket connector D1is shown, and featured a solder ball encampment D19 at a mountingsurface D10 a of the socket connector D1.

The solder ball encampment D19 is a structure integrally formed belowthe mounting surface D10 a and slightly narrows the passageway D11 inits lower end, as typically shown in FIG. 19. The encampment D19 is infact an extension D19 formed on the mounding surface D10 a which extendsacross over a side wall D11 a of the passageway D11 opposite to thecurvilinear lobe D26. The extension D19 basically narrows down the loweropening of the passageway D11. The extension D19 a further includes aninclined surface D19 a opened outward. As shown in the dotted line, thesolder ball D30 can be readily and securely encamped between thecurvilinear lobe D27 and the inclined surface D19 a of the extensionD19. On the other hand, it can be readily appreciated from FIG. 19 thata Center of the solder ball D30 is located above from a line drawn froma tip D19 b of the inclined surface D19 a, and the tip D26 a of thecurvilinear lobe D26.

In addition, in this embodiment, the wave arrangement D27, whichincludes a peak D271, a first slope D272, and a second slope D273,generally includes a second and auxiliary peak D274 at the first slopeD271 moving the tip D26 a of the curvilinear lobe D26 closer to thesolder ball D30, if the second peak D274 is not formed. As clearly shownin FIG. 19, the inclined surface D19 a and the formation of the peakD271 jointly prevent the solder ball D30 from going further into thepassageway D11. As one of issues encountered by the mechanicalattachment of the solder ball D30 is accidentally pushing the solderball D30 into the passageway D11. As shown in FIGS. 11 through 13 ofU.S. Pat. No. 6,024,584 issued to Lemke on Feb. 15, 2000, a partitionwithin the passageway is formed to prevent the solder ball from furtherinto the passageway. U.S. Pat. No. 6,042,389 issued to Lemke on Mar. 28,2000 discloses a similar design, such as shown in FIGS. 4 and 5. Whilein U.S. Pat. No. 6,572,397 issued to Ju on Jun. 3, 2003, a lower portionof a contact is formed into a cap shape to hold and limit the solderball, as shown in FIGS. 6 and 11. In comparison, the use of thearrangement of curvilinear lobe D26, the wave arrangement D27, and theencampment D19 properly secure the solder ball D30 therebetween, andeven ensure a reliable and robust tear-shaped solder joint, such asshown in FIG. 10 of the present invention. On the other hand, the peakD272 and the extension D19 jointly define a narrow passage entering thepassageways D11 from mounting surface D10 a.

As still referring to FIG. 18, a bottom view of the socket connector D1,it can be readily seen that along with the encampment D19 is a pluralityof disks D10 c 1, D10 c 2, and D10 c 3, typically reference marked. Asit can be readily see from FIG. 18, the extension D19 is in factarranged between the disks D10 c 1, D10 c 3 and D10 c 2, D10 c 4. Theprovision of the disks D10 c 1, D10 c 3 and D10 c 2, D10 c 4 smooth theformation of the passageway D11 during the molding process. In addition,the disks D10 c 1 and D10 c 4 can be selectively hollowed so as tocontrol warpage of the housing D10.

FIG. 20 illustrates the socket connector D1 in full with a portion ofcontact terminals D20 is shown. It can be readily appreciated that thesocket connector D1 includes an insulative housing D10 with a pluralityof passageways D11 defined between a mating interface D10 b, and amounting surface D10 a. Peripheral walls D10 d surrounds the matinginterface D10 b therefore defining a cavity D10 e for receiving an ICpackage, i.e. the so-called CPU. The peripheral walls D10 d is furtherdefines with notches D10 f for easy accessing of the CPU to have itremoved from the cavity D10 e.

FIG. 21 illustrates a bottom of the socket connector D1 in portion. Itcan be seen that the disks D10 c 1, D10 c 3 and D10 c 2, D10 c 4 can beserved as a standoff on the mounting surface D10 a for properlysupporting the socket connector D1 after the solder ball D30 is melted.

FIGS. 22, 23 and 26 illustrate an electrical connector in accordancewith a fifth embodiment which comprises an insulative housing E10 and aplurality of contacts E20 received in the insulative housing E10. Pleasereferring to FIGS. 23-24, the contact E20 has a plate-like base portionE21 with a plurality of barbs at opposite sides thereof, a retainingsection E22 extending upwardly from the base portion E21, and a contactengaging arm E23 projecting upwardly from the base portion E21 with acontact tip E24 at a top end thereof. A solder portion E25 extendsdownwardly from the base portion E21 and has an upper wave arrangementE27 and a lower tail E26 extending downwardly and laterally from thewave arrangement E27. The wave arrangement E27 and the contact engagingarm E23 are located at a same side of the base portion E21. The tail E26contacts with a solder ball E30 at a point E260 thereof for securing thesolder ball E30.

With reference of FIGS. 22-27, the insulative housing E10 has oppositeupper and lower surfaces E13, E15 and a plurality of through holesextending therethrough. The through holes in one row are staggered withthe through hole in an adjacent row. The through hole includes apassageway E11 and a retaining slot E12 communicated with each other anddefining an inner step surface E14 facing the lower surface E15. Thebase portion E21 and the retaining portion E22 are arranged at a firstof the passageway E11. The retaining slot E12 has a vertical surfaceE120 and a slant surface E121 facing opposite to the vertical surfaceE120. The tail E26 is located adjacent to the vertical surface wherebyforming a deforming space E123 so that the tail E26 can move laterallyfor disposing the solder ball E30. A receiving space E124 is formedbetween the tail E26 and the slant surface E121 for receiving the solderball E30. The slant surface E121 has two contact points E1211, E1212abutting with the solder ball E30 a lower points E1212 is below a centerC of the solder ball E30 and an upper point E1211 is higher than thecenter C. The base portion E21 and the solder portion E25 are disposedbetween the first side of the through hole and a vertical line VLpassing though the center C of the solder ball E30.

The tail E26 projects to the first side of the through hole, and thewave arrangement E27 projects from the base portion E21 to a second sideof the through hole opposite to the first side. The wave arrangement E27defines a peak E271 and two curvilinear lobes E272, E273 at oppositesides of the peak E271. The two curvilinear lobes E272, E273 areconnected with the base portion E21 and the tail E26. The base portionE21 and the wave arrangement E27 are received in the passageway E11, andthe tail E26 and solder ball E30 are disposed in the retaining slot E12.The contact engaging arm E23 extends beyond the upper surface E13, andthe tail E26 and the solder ball E30 extend out of the lower surfaceE15.

As disclosed FIGS. 6-27, the base portion and the solder portion aredisposed between on one side of the insulative housing and a verticalline passing though a center of the solder ball. The wave arrangement orthe tail/curvilinear lobe each defines a space with the insulativehousing so that the contact deforms and the tail/curvilinear lobe movesin the through hole. Then the tail/curvilinear lobe and the insulativehousing define an entrance for the solder ball.

When the solder ball is inserted, the tail/curvilinear lobe has anelastic deformation thereby enlarging the entrance so that the solderball passing. Then the tail/curvilinear lobe defined by thetail/curvilinear lobe and an inner surface of the through hole so thanthe solder ball can be inserted in the receiving space and clasped bythe tail/curvilinear lobe and the insulative housing. That is to say,before inserting the solder ball, the tail/curvilinear lobe is locatedat a first position which is shown by the dotted line in FIG. 27A.During the insertion of the solder ball, the tail/curvilinear lobe isdeformed and moves to enlarge the entrance by the solder ball. Thetail/curvilinear lobe has a biggest deformation at a second position asshown by the solid line of FIG. 27A. Then the solder ball can beinserted until it is clasped by the tail/curvilinear lobe and theinsulative housing. At this time, the tail/curvilinear lobe is locatedat a third position which is located between the first and positions asshown in FIG. 27B.

Since the tail/curvilinear lobe and the solder ball has at least onecontact point below a center of the solder ball thereby provides anupward supporting force of the solder ball. The inner surface of thethrough hole and the solder ball has at least one contact point on thetop of the center of the solder ball which prevents the solder ball frommove upwardly. Moreover, the tail/curvilinear lobe and the insulativehousing located at opposite sides of the solder ball further limit ahorizontal movement of the solder ball.

It will be understood that the invention may be embodied in otherspecific forms without departing from the spirit or centralcharacteristics thereof. The present examples and embodiments,therefore, are to be considered in all respects as illustrative and notrestrictive, and the invention is not to be limited to the details givenherein.

1. An electrical connector comprising: an insulative housing havingopposite upper and lower surfaces and a plurality of through holesextending through the upper surface to the lower surface; a plurality ofcontacts assembled to the insulative housing and each including avertical base portion secured to a first side of the through hole, acontact engaging arm extending from a top end of the base portion, and asolder portion extending from a bottom end of the base portion, saidsolder portion including a wave arrangement below the base portion andprojecting from the base portion to a second side of the through holewhich opposites to said first side, and a tail extending downwardly fromthe wave arrangement and capable of moving from the first side to thesecond side; and a plurality of solder balls disposed in the thoughholes and each is clasped by the tail and insulative housing.
 2. Theelectrical connector as claimed in claim 1, wherein the wave arrangementdefines a peak and two curvilinear lobes at opposite sides of the peak,and wherein the two curvilinear lobes are connected with the baseportion and the tail.
 3. The electrical connector as claimed in claim 2,wherein the through hole comprises an upper passageway and a lowerretaining slot communicated with each other and defines a step surfacetherebetween facing the lower surface of the insulative housing.
 4. Theelectrical connector as claimed in claim 3, wherein the base portion andthe wave arrangement are received in the passageway and the tail isconfigured to an arc shape, and wherein the tail extends from the stepsurface and projects out of the lower surface.
 5. The electricalconnector as claimed in claim 1, wherein the base portion and the solderportion are disposed between the first side of the through hole and avertical line passing though a center of the solder ball.
 6. Theelectrical connector as claimed in claim 3, wherein the wave arrangementand a vertical surface of the passageway define a first space at thefirst side of the through hole.
 7. The electrical connector as claimedin claim 3, wherein the tail and a vertical surface of the retainingslot define a second space at the first side of the through hole.
 8. Theelectrical connector as claimed in claim 1, wherein the tail and thesolder ball has at least one contact point, and wherein said at leastone contact point is below a center of the solder ball; and theinsulative housing and the solder ball has at least one contact point,and wherein said at least one contact point is higher than a center ofthe solder ball.
 9. An electrical connector comprising: an insulativehousing having opposite upper and lower surfaces and a plurality ofthrough holes extending through the upper surface to the lower surface,the through hole comprising an upper passageway and a lower retainingslot communicated with each other; a plurality of contacts assembled tothe insulative housing and each including a base portion secured in thepassageway, a contact engaging arm extending upwardly from the baseportion, and a solder portion extending downwardly from the baseportion, said solder portion including a wave arrangement connected withthe base portion and a tail extending downwardly from the wavearrangement; and a plurality of solder members secured by one side ofthe retaining slot and the tail, and the tail and the other side of theretaining slot define a deforming space so that the tail can move to theother side of the retaining slot to dispose the solder member.
 10. Theelectrical connector as claimed in claim 9, wherein the wave arrangementprojects downwardly and laterally from the base portion, and the tailproject downwardly from the wave arrangement.
 11. The electricalconnector as claimed in claim 10, wherein the wave arrangement defines apeak and two curvilinear lobes at opposite sides of the peak, andwherein the two curvilinear lobes are connected with the base portionand the tail.
 12. The electrical connector as claimed in claim 9,wherein the tail is configured to a curvilinear lobe and extending alongan outer surface of the solder member.
 13. The electrical connector asclaimed in claim 9, wherein the passageway and the retaining slot definea step surface therebetween and facing the lower surface, and the wavearrangement is located in the passageway.
 14. The electrical connectoras claimed in claim 9, wherein the base portion and the solder portionare disposed between one side of the through hole and a vertical linepassing though a center of the solder member.
 15. The electricalconnector as claimed in claim 9, wherein the tail and the solder memberhas at least one contact point, and wherein said at least one contactpoint is below a center of the solder member, and the insulative housingand the solder member has at least one contact point, and wherein saidat least one contact point is higher than a center of the solder member.16. An electrical connector for connecting an electronic package and aprinted circuit board, comprising: an insulative housing defining aplurality of passageways extending therethrough in a vertical directionbetween opposite upper and lower surfaces thereof; and a plurality ofcontacts disposed in the corresponding passageways, respectively, eachof said contacts defining a base portion retaining to the housing, anupper contacting section extending upwardly from the base portion andbeyond the upper surface for contacting the electronic package, a tailsection extending downwardly from the base portion to hold a solder ballfor connecting to the printed circuit board, wherein in a side view, ineach passageway and for each of solder ball the housing provides spacedfirst and second contact points and the tail section of thecorresponding contact provides a third contact point for holding thesolder ball in position between the tail section of the correspondingcontact and the housing.
 17. The electrical connector as claimed inclaim 16, wherein in each of the passageways, the housing defines afirst side wall against which the base portion abuts and around whichthe tail section extends, and a second side wall opposite to the firstside wall, under condition that the first and second contact points arelocated around the second side wall.
 18. The electrical connector asclaimed in claim 17, wherein the first contact point is located abovethe second contact point, and the first contact point is located closerto a vertical center line of the solder ball than the second contactpoint.
 19. The electrical connector as claimed in claim 18, wherein ineach of the contacts, the tail section extends from the base portion viaa wavy section.
 20. The electrical connector as claimed in claim 18,wherein in each of the contacts, the tail section defines a curvedconfiguration compliantly clamping the corresponding solder ball.